U.S. patent application number 12/392719 was filed with the patent office on 2009-08-27 for semicondcutor nanoparticle capping agents.
This patent application is currently assigned to NANOCO TECHNOLOGIES LIMITED. Invention is credited to Siobhan Cummins, Steven M. Daniels, Mark C. McCairn, Nigel Pickett.
Application Number | 20090212258 12/392719 |
Document ID | / |
Family ID | 40626894 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090212258 |
Kind Code |
A1 |
McCairn; Mark C. ; et
al. |
August 27, 2009 |
SEMICONDCUTOR NANOPARTICLE CAPPING AGENTS
Abstract
Embodiments of the invention involve semiconductor nanoparticle
capping ligands, their production and use. Ligands may have the
formula ##STR00001## with m ranging from approximately 8 to
approximately 45. An embodiment provides a method of forming a
compound of the formula ##STR00002## including the steps of
providing a first starting material comprising poly(ethyleneglycol)
and reacting the first starting material with a second starting
material comprising a functional group for chelating to the surface
of a nanoparticle to thereby form the compound.
Inventors: |
McCairn; Mark C.; (Newent,
GB) ; Daniels; Steven M.; (Manchester, GB) ;
Cummins; Siobhan; (Ludlow, GB) ; Pickett; Nigel;
(London, GB) |
Correspondence
Address: |
GOODWIN PROCTER LLP;PATENT ADMINISTRATOR
53 STATE STREET, EXCHANGE PLACE
BOSTON
MA
02109-2881
US
|
Assignee: |
NANOCO TECHNOLOGIES LIMITED
Manchester
GB
|
Family ID: |
40626894 |
Appl. No.: |
12/392719 |
Filed: |
February 25, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61031218 |
Feb 25, 2008 |
|
|
|
Current U.S.
Class: |
252/301.36 ;
528/421 |
Current CPC
Class: |
C07C 51/367 20130101;
C08G 65/3344 20130101; C08G 65/3322 20130101; C07C 59/125 20130101;
C08G 65/33341 20130101; C08G 65/337 20130101; C08G 65/33306
20130101; C07C 51/367 20130101; C07C 59/125 20130101 |
Class at
Publication: |
252/301.36 ;
528/421 |
International
Class: |
C09K 11/08 20060101
C09K011/08; C08G 65/04 20060101 C08G065/04; C09K 11/02 20060101
C09K011/02 |
Claims
1. A ligand having the formula: ##STR00020## wherein m ranges from
8 to 45.
2. The ligand of claim 1 disposed proximate a core of a
nanoparticle.
3. The ligand of claim 2, wherein the core of the nanoparticle
comprises at least one semiconductor material.
4. The ligand of claim 1 disposed proximate a shell of a
nanoparticle.
5. The ligand of claim 4, wherein the shell of the nanoparticle
comprises at least one semiconductor material.
6. The ligand of claim 1 disposed within a solvent, the solvent
further comprising at least one nanoparticle precursor
material.
7. A method of forming a compound of the formula ##STR00021##
wherein X is an atom or chemical group, Y is an atom or chemical
group and m is an integer, the method comprising the steps of:
providing a first starting material comprising
poly(ethyleneglycol); and reacting the first starting material with
a second starting material comprising a functional group for
chelating to the surface of a nanoparticle, thereby forming the
compound.
8. The method of claim 7, wherein the first starting material
comprises a terminal hydroxyl group, the second starting material
comprises a leaving group, and reacting the first and second
starting materials comprises detaching the leaving group.
9. The method of claim 7, further comprising capping at least one
nanoparticle with the compound.
10. A method for producing capped nanoparticles comprising capping
at least one nanoparticle with a compound of formula ##STR00022##
wherein X is an atom or chemical group, Y is an atom or chemical
group and m is an integer.
11. The method of claim 7, wherein X is selected from the group
consisting of H, CH.sub.3, and --CH.sub.2CO.sub.2H.
12. The method of claim 7, wherein Y is selected from the group
consisting of p-toluene sulphonate, carboxyl, --CH.sub.2CO.sub.2H,
-PhCO.sub.2H, -SiPh.sub.2.sup.tBu, phenyl, --CH.sub.2Ph, thiol,
amino, dithiocarbamato, phosphonic acid, phosphinic acid, vinyl,
acetylene, aryl, and heteroaryl.
13. The method of claim 7, wherein m ranges from 8 to 45.
14. The method of claim 7, wherein the at least one nanoparticle
comprises at least one semiconductor material.
15. Nanoparticles capped with a compound of formula ##STR00023##
wherein X is an atom or chemical group, Y is an atom or chemical
group and m is an integer.
16. Nanoparticles according to claim 15, wherein X is selected from
the group consisting of H, CH.sub.3, and --CH.sub.2CO.sub.2H.
17. Nanoparticles according to claim 15, wherein Y is selected from
the group consisting of p-toluene sulphonate, carboxyl,
--CH.sub.2CO.sub.2H, -PhCO.sub.2H, -SiPh.sub.2.sup.tBu, phenyl,
--CH.sub.2Ph, thiol, amino, dithiocarbamato, phosphonic acid,
phosphinic acid, vinyl, acetylene, aryl, and heteroaryl.
18. Nanoparticles according to claim 15, wherein m ranges from 8 to
45.
19. Nanoparticles according to claim 15, wherein at least one of
the nanoparticles comprises at least one semiconductor
material.
20. A display device comprising: a plurality of nanoparticles, each
capped with a ligand having the formula ##STR00024## wherein m is
an integer, disposed within a material substantially transparent to
light.
21. The display device of claim 20, further comprising means for
exciting the plurality of nanoparticles such that the nanoparticles
can emit visible light.
22. The display device of claim 20, wherein each of the plurality
of nanoparticles comprises: a core comprising a first semiconductor
material; and a shell comprising a second semiconductor material
different from the first semiconductor material.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of and priority to
co-pending U.S. Provisional Patent Application No. 61/031,218,
filed Feb. 25, 2008, the entire contents of which are herein
incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention relates to semiconductor nanoparticle capping
ligands, their production and their use in preparing functionalized
semiconductor nanoparticles.
BACKGROUND
[0003] The size of a semiconductor nanoparticle helps determine the
electronic properties of the material; the bandgap energy may be
inversely proportional to the size of the semiconductor
nanoparticle as a consequence of quantum confinement effects. In
addition, the large surface area to volume ratio of the
nanoparticle affects the physical and chemical properties of the
nanoparticle.
[0004] Single-core nanoparticles that include a single
semiconductor material typically have relatively low quantum
efficiencies. These low quantum efficiencies arise from
non-radiative electron-hole recombinations that occur at defects
and dangling bonds at the surface of the nanoparticle.
[0005] Core-shell nanoparticles typically include a single
semiconductor core material that has a shell of a second
semiconductor material grown epitaxially on the surface of the
core. The shell material usually has a wider bandgap and similar
lattice dimensions to the core semiconductor material. The
intention of adding the shell may be to eliminate defects and
dangling bonds from the surface of the core, and thereby confine
charge carriers within the core and away from surface states that
may function as centers for non-radiative recombination.
[0006] Still, the surfaces of core, core-shell, and core-multishell
nanoparticles may have highly reactive dangling bonds. These may be
be passivated by capping the surface atoms with organic ligand
molecules that inhibit aggregation of particles, protect the
particle from its surrounding chemical environment, and (at least
in the case of core nanoparticles) provide electronic
stabilization. The capping ligand compound may be the solvent that
is employed in the core growth and/or shelling of the
nanoparticles. Alternatively, the capping ligand may be dissolved
in an inert solvent and then used in the core growth and/or
shelling of the nanoparticles. Either way, the ligand compound caps
the surface of the nanoparticle by donating lone-pair electrons to
the surface metal atoms of the nanoparticle.
[0007] Nanoparticles may typically be synthesized in the presence
of a lipophilic ligand compound, resulting in nanoparticles that
may be soluble in non-polar media. To decrease or eliminate this
solubility, the ligand compound may be exchanged for a different
ligand compound of greater polarity; however, the quantum yield of
the nanoparticles diminishes as a result.
[0008] The resulting semiconductor nanoparticles may be used in a
range of different applications, in which the nanoparticles may be
externally excited by photo-excitation, electro-excitation, or
another form of excitation, leading to electron-hole recombination
and subsequent emission of photons in the form of light of a
predetermined wavelength, e.g., visible light. The use of surface
functionalized nanoparticles in such applications has so far,
however, been limited by the loss in quantum yield upon surface
functionalization.
SUMMARY
[0009] Disclosed herein are methods that may obviate or mitigate
one or more of the above problems with current methods for
producing surface functionalized semiconductor nanoparticles.
[0010] Some embodiments provide for the fabrication of capping
ligands for semiconductor nanoparticles as well as the precursors
of the capping ligands. The capping ligands disclosed herein may be
utilized in and during the synthesis of the nanoparticles,
resulting in nanoparticles of high quantum yield and polarity. The
resulting semiconductor nanoparticles may be used in a range of
different applications, such as display applications whereby the
semiconductor nanoparticles may be incorporated into a device or
transparent material; or incorporation into polar solvents (e.g.,
water and water-based solvents). The resulting nanoparticles may
also be incorporated into inks, polymers or glasses; or attached to
cells, biomolecules, metals, molecules and the like. The compounds
and methods disclosed herein thus overcome the problems with prior
art methods for the surface functionalization of semiconductor
nanoparticles which have previously hindered the use of surface
functionalized nanoparticles in such applications.
[0011] In an aspect, an embodiment of the invention includes a
ligand having the formula
##STR00003##
with m ranging from 8 to 45.
[0012] One or more of the following features may be included. The
ligand may be proximate a core or a shell of a nanoparticle. The
core of the nanoparticle may have at least one semiconductor
material. The ligand may be disposed within a solvent having at
least one nanoparticle precursor material.
[0013] In another aspect, an embodiment of the invention includes a
method of forming a compound of the formula
##STR00004##
where X is an atom or chemical group, Y is an atom or chemical
group and m is an integer. A first starting material including
poly(ethyleneglycol) is provided, and the first starting material
is reacted with a second starting material having a functional
group for chelating to the surface of a nanoparticle, thereby
forming the compound.
[0014] One or more of the following features may be included. The
first starting material has a terminal hydroxyl group, the second
starting material has a leaving group, and reacting the first and
second starting materials includes detaching the leaving group. At
least one nanoparticle may be capped with the compound. Variable X
may be selected from H, CH.sub.3, and --CH.sub.2CO.sub.2H. Variable
Y may be selected from p-toluene sulphonate, carboxyl,
--CH.sub.2CO.sub.2H, -PhCO.sub.2H, -SiPh.sub.2.sup.tBu, phenyl,
--CH.sub.2Ph, thiol, amino, dithiocarbamato, phosphonic acid,
phosphinic acid, vinyl, acetylene, aryl, and heteroaryl. Variable m
may range from 8 to 45. At least one nanoparticle may include at
least one semiconductor material.
[0015] In another aspect, an embodiment of the invention includes a
method for producing capped nanoparticles including capping at
least one nanoparticle with a compound of formula
##STR00005##
where X is an atom or chemical group, Y is an atom or chemical
group and m is an integer.
[0016] In yet another aspect, embodiments of the invention include
nanoparticles capped with a compound of formula
##STR00006##
where X is an atom or chemical group, Y is an atom or chemical
group and m is an integer.
[0017] One or more of the following features may be included.
Variable X may be H, CH.sub.3, and/or --CH.sub.2CO.sub.2H. Variable
Y may be selected from p-toluene sulphonate, carboxyl,
--CH.sub.2CO.sub.2H, -PhCO.sub.2H, -SiPh.sub.2.sup.tBu, phenyl,
--CH.sub.2Ph, thiol, amino, dithiocarbamato, phosphonic acid,
phosphinic acid, vinyl, acetylene, aryl, and/or heteroaryl.
Variable m may range from 8 to 45. At least one nanoparticle may
include at least one semiconductor material.
[0018] In another aspect, an embodiment of the invention includes a
display device having a plurality of nanoparticles, each capped
with a ligand having the formula
##STR00007##
where m is an integer, disposed within a material substantially
transparent to light.
[0019] One or more of the following features may be included. The
display device may include means for exciting the plurality of
nanoparticles such that the nanoparticles can emit visible light.
Each of the plurality of nanoparticles may have a core including a
first semiconductor material and a shell including a second
semiconductor material different from the first semiconductor
material.
BRIEF DESCRIPTION OF THE FIGURE
[0020] FIG. 1 schematically illustrates a quantum dot
nanoparticle.
DETAILED DESCRIPTION
[0021] One embodiment provides for the preparation and use of a
compound of the following formula in the production and capping of
quantum dot nanoparticles:
##STR00008##
where m may be between 0 and approximately 4500, such as between 0
and approximately 450, or even such as 0 and approximately 17. In
some embodiments, m may be approximately 8, approximately 13,
approximately 17, or approximately 45. These compounds may be
suitable for use as a ligand compound (i.e., a capping agent) for
core growth and/or shelling of quantum dot nanoparticles.
[0022] One embodiment provides a ligand having the formula
##STR00009##
with m ranging from approximately 8 to approximately 45.
[0023] In one embodiment, the ligand is disposed proximate a core
of a nanoparticle, where the core may include at least one
semiconductor material. In a further embodiment, the ligand is
disposed proximate a shell of a nanoparticle, the shell optionally
including at least one semiconductor material. The ligand may be
disposed within a solvent, in which case the solvent may further
include at least one nanoparticle precursor material.
[0024] One embodiment of the invention relates to methods of
synthesizing a compound of formula:
##STR00010##
where m may be as defined above, X is selected from the group
consisting of H, --CH.sub.3, and --CH.sub.2CO.sub.2H, and Y is
selected from the group consisting of p-toluene sulphonate,
carboxyl (e.g. --CH.sub.2CO.sub.2H or -PhCO.sub.2H),
-SiPh.sub.2.sup.tBu, phenyl (e.g., --CH.sub.2Ph), thiol, amino,
dithiocarbamato, phosphonic acid, phosphinic acid, vinyl,
acetylene, aryl, heteroaryl, and the like.
[0025] Another embodiment provides for a method of forming a
compound of the formula
##STR00011##
where the method includes the steps of providing a first starting
material including poly(ethyleneglycol), and reacting the first
starting material with a second starting material that includes a
functional group for chelating to the surface of a nanoparticle,
thereby forming the compound.
[0026] The first starting material may include a terminal hydroxyl
group, the second starting material may include a leaving group,
and the step of reacting the first and second starting materials
may include detaching the leaving group.
[0027] In another embodiment, the method further includes capping
at least one nanoparticle with the compound. Accordingly, another
embodiment relates to a method for producing capped nanoparticles
including carrying out the method described above and then capping
at least one nanoparticle with the resulting compound of
formula
##STR00012##
as defined above. Moreover, a further embodiment provides
nanoparticles capped with a compound of formula
##STR00013##
as defined above.
[0028] In another embodiment, the invention relates to a display
device including a plurality of nanoparticles, each capped with a
ligand having the formula
##STR00014##
disposed within a material substantially transparent to light. The
display device may include means for exciting the plurality of
nanoparticles such that the nanoparticles emit visible light.
Moreover, each of the plurality of nanoparticles may include a core
including a first semiconductor material, and a shell including a
second semiconductor material different from the first
semiconductor material.
[0029] The above defined methods may include the steps of coupling,
to an appropriately functionalized molecule of the formula X--W,
the hydroxyl functionality of a poly(ethyleneglycol) starting
material having the formula:
##STR00015##
where m is as defined above, and Z is selected from the group
consisting of H or --CH.sub.3. X is selected from the group
consisting of a leaving group such as a halogen, p-toluene
sulphonate, mesyl (CH.sub.3--S(O).sub.2--O--) or a nucleophile such
as OH, and W is a suitable functional group to chelate to the
surface of a nanoparticle, such as a carboxyl or thio group.
[0030] Z may be pre-functionalized to include a head group to
afford the desired solubility to nanoparticles capped with the
ligand produced as a result of the reaction of X--W with
##STR00016##
or Z may be subject to post-reaction modification so that it
incorporates the desired head group, such as, but not limited to
p-toluene sulphonate, carboxyl (e.g. --CH.sub.2CO.sub.2H or
-PhCO.sub.2H), -SiPh.sub.2.sup.tBu, phenyl (e.g. --CH.sub.2Ph),
thiol, amino, dithiocarbamato, phosphonic acid, phosphinic acid,
vinyl, acetylene, aryl, heteroaryl, and the like.
[0031] In one embodiment, the ligand has the formula:
##STR00017##
where X is --CH.sub.3 and m is approximately 8 in both the
poly(ethyleneglycol) methyl ether (.about.350) starting material
and ligand compound. Y is H in the poly(ethyleneglycol) methyl
ether (having a molecular weight of approximately 350) starting
material and Y is --CH.sub.2CO.sub.2H in the ligand compound.
[0032] Further embodiments provide semiconductor quantum dot
nanoparticles incorporating the capping ligands defined above and
methods for producing the same employing standard synthetic methods
for binding such ligands to the nanoparticle surface.
[0033] The semiconductor material included in the nanoparticles
capped with the above-defined capping ligands may incorporate ions
from any one or more of groups 2 to 16 of the periodic table,
including binary, ternary and quaternary materials, that is,
materials incorporating two, three or four different ions
respectively. By way of example, the nanoparticles may incorporate
a core semiconductor material, such as, but not limited to, CdS,
CdSe, CdTe, ZnS, ZnSe, ZnTe, InP, InAs, InSb, AIP, AIS, AIAs, AISb,
GaN, GaP, GaAs, GaSb, PbS, PbSe, Si, Ge and combinations thereof.
Nanoparticles may possess cores with mean diameters of less than
around 20 nm, such as less than around 15 nm and further such as in
the range of around 2 nm to around 5 nm.
[0034] As mentioned above, in order to at least partially address
issues related to non-radiative electron-hole recombinations that
occur at defects and dangling bonds at the nanoparticle surface
resulting in undesirably low quantum efficiencies, nanoparticle
cores may be at least partially coated with one or more layers
(also referred to herein as "shells") of a different material to
the core, for example, a semiconductor material. Thus, the
nanoparticles capped using ligands disclosed herein may incorporate
one or more shell layers. The material included in the or each
shell may incorporate ions from any one or more of groups 2 to 16
of the periodic table. Where a nanoparticle includes two or more
shells, each shell may be formed of a different material. In an
exemplary core/shell material, the core may be formed from one of
the materials specified above and the shell may include a
semiconductor material of larger band-gap energy and similar
lattice dimensions to the core material. Example shell materials
include, but are not limited to, ZnS, MgS, MgSe, MgTe and GaN. The
confinement of charge carriers within the core and away from
surface states provides quantum dots of greater stability and
higher quantum yield. It will be appreciated that where two
materials may be provided in adjacent layers of a semiconductor
nanoparticle whose lattice structures do not correspond closely, it
may be appropriate to ease any lattice strain that exists at the
interface of the two materials by introducing a graded layer in
between the two layers of material. The graded layer will typically
include most, if not all, of the ions in each of the two adjacent
layers but the proportions of the ions will vary from the core to
the shell. The region of the graded layer adjacent to the core will
include a majority of at least one of the ions in the core
material, and the region of the graded layer adjacent to the shell
will include a majority of the at least one of the ions in the
shell material.
[0035] The mean diameter of quantum dot nanoparticles, which may be
capped using the ligands disclosed herein, may be varied to modify
the emission wavelength. The energy levels and hence the frequency
of the quantum-dot fluorescence emission may be controlled by the
material from which the quantum dot is made and the size of the
quantum dot. Generally, quantum dots made of the same material have
a more pronounced red emission the larger the quantum dot. In some
embodiments, the quantum dots have diameters of around 1 nm to
around 15 nm, such as around 1 nm to around 10 nm. The quantum dots
preferably emit light having a wavelength of around 400 nm to
around 900 nm, such as around 400 nm to around 700 nm.
[0036] Typically, as a result of the core and/or shelling
procedures employed to produce the core, core/shell or
core/multishell nanoparticles, the nanoparticles are at least
partially coated with a surface binding ligand, such as myristic
acid, hexadecylamine and/or trioctylphosphineoxide. Such ligands
may typically be derived from the solvent in which the core and/or
shelling procedures were carried out. While ligands of this type
may increase the stability of the nanoparticles in non-polar media,
provide electronic stabilization and/or negate undesirable
nanoparticle agglomeration, as mentioned previously, such ligands
usually prevent the nanoparticles from stably dispersing or
dissolving in more polar media, such as aqueous solvents.
[0037] In some embodiments, quantum dots may be included that are
aqueous-compatible, stable, small and of high quantum yield (see
FIG. 1). Where lipophilic surface binding ligand(s) are coordinated
to the surface of the quantum dots as a result of the core and/or
shelling procedures (examples include hexadecylamine,
trioctylphosphineoxide, myristic acid), such ligands may be
exchanged entirely or partially with ligands disclosed herein using
standard methods known to the skilled person, or the ligands
disclosed herein may interchelate with the existing lipophilic
surface binding ligands, again using standard methods.
[0038] Embodiments of the invention will now be illustrated by the
following examples, which are given for the purpose of illustration
only and without any intention of limiting the scope of the present
invention.
EXAMPLES
[0039] Glassware was dried (120.degree. C.) in an oven overnight.
Dichloromethane ("DCM") and triethylamine ("TEA") were distilled
from calcium hydride after heating at reflux for at least 1 hour.
Tetrahydrofuran was distilled from Na/benzophenone after heating at
reflux for at least 1 hour. Poly(ethylene glycols) were heated at
120.degree. C. under high vacuum for 1 hour. All other reagents
were used as received from a commercial supplier. All reaction
mixtures were stirred magnetically and conducted under an
atmosphere of dinitrogen gas.
Example 1
Synthesis of monomethyl ether poly(oxyethylene qlycol).sub.350
phthalimide
[0040] A. Synthesis of poly(oxyethylene glycol).sub.350 monomethyl
ether p-toluene sulfonate
##STR00018##
[0041] A solution of TsCl (27.792 g, 143.00 mmol) in DCM (80 mL)
was added drop-wise over 2 hours to an ice-cooled solution of
poly(oxyethylene glycol).sub.350 monomethyl ether (50.000 g, 143.00
mmol), triethylamine (40.30 mL, 290.0 mmol), and DMAP (0.177 g, 1.4
mmol) in DCM (75 mL), and the resultant mixture was left to stir
overnight while warming to room temperature. The reaction mixture
was washed with distilled water (2.times.200 mL), saturated sodium
bicarbonate solution (2.times.100 mL), saturated citric acid
solution (2.times.100 mL), dried over anhydrous sodium sulphate,
filtered and concentrated under reduced pressure to give a
yellow-colored oil. This oil was dissolved in hexane (3.times.200
mL) and the unreacted TsCl was separated from the reaction mixture
by filtration. The filtrate was concentrated under reduced pressure
to provide poly(oxyethylene glycol).sub.350 monomethyl ether
p-toluene sulfonate as a pale yellow-colored oil.
B. Synthesis of monomethyl ether poly(oxyethylene glycol).sub.350
phthalimide
##STR00019##
[0042] Potassium phthalimide (2.679 g, 14.48 mmol) was added to a
solution of poly(oxyethylene glycol).sub.350 monomethyl ether
p-toluene sulfonate (5.000 g, 9.65 mmol) in DMF (45 mL)/water (6
mL) and then stirred overnight (80.degree. C.).
[0043] The reaction mixture was allowed to cool to room
temperature, dissolved in DCM (100 mL) and washed sequentially with
distilled water (6.times.500 mL), saturated brine (6.times.500 mL)
(to remove DMF), distilled water (500 mL), then dried over
anhydrous magnesium sulphate, filtered and concentrated under
reduced pressure. The resultant oil was dissolved in the minimum
volume of DCM, filtered, and then concentrated under reduced
pressure to give monomethyl ether poly(oxyethylene glycol).sub.350
phthalimide.
[0044] The phthalimide group of the monomethyl ether
poly(oxyethylene glycol).sub.350 phthalimide compound is an example
of a terminal functional group that may be conveniently converted
into another group (such as an amino group, e.g. --NH.sub.2, when
treated with a base) to confer to the resulting ligand the ability
to bind to the surface of nanoparticles and/or the ability to
modify the solubility of nanoparticles to which the ligand is
bound.
Example 2
Synthesis of poly(oxyethylene glycol).sub.350 monomethyl ether
acetic acid
[0045] A solution of bromoacetic acid (162.83 g, 1.1719 moles) in
tetrahydrofuran (500 mL) was added dropwise to a suspension of
sodium hydride (93.744 g, 2.3436 moles) in tetrahydrofuran (500 mL)
that was stirred and cooled (0.degree. C.). Poly(oxyethylene
glycol).sub.350 monomethyl ether that had previously been dried
(120.degree. C., high vacuum, 1 hour) was dissolved in
tetrahydrofuran (150 mL) and added dropwise to the reaction
mixture. The reaction mixture was stirred while warming to room
temperature overnight.
[0046] The reaction mixture was poured over ice, acidified (pH=1)
and then concentrated under reduced pressure to give a white solid
suspended in a yellow-colored oil. The oil was dissolved in
CH.sub.2Cl.sub.2 (2.5 L) and the white solid was separated by
filtration. The filtrate was washed with saturated NaHCO.sub.3
(5.times.50 mL) and then concentrated under reduced pressure to
give a yellow-colored oil. The oil was dissolved in water (2 L) and
washed with diethyl ether (5.times.50 mL). The aqueous phase (pH of
approximately 3) was acidified with 1M HCl.sub.(aq) to pH of
approximately 1 and washed with diethyl ether (50 mL). The aqueous
phase was concentrated under reduced pressure to give a colorless
oil (298.78 g).
Example 3
Capping of Quantum Dots
[0047] Representative quantum-dot materials compatible with
embodiments disclosed herein include CdSe, GaAs, InAs, InP,
CuInS.sub.2, CuInSe.sub.2, and CuIn.sub.1-xGa.sub.xSe.sub.2.
Nanoparticle synthesis may be carried out using techniques
described, for example, in U.S. Pat. No. 6,379,635 and co-pending
U.S. patent application Ser. Nos. 11/579,050 and 11/588,880. The
nanoparticles may be characterized by any conventional technique
(e.g., XRD, UV/Vis/Near-IR spectrometry, SEM, TEM, EDAX,
photoluminescence spectrometry, elemental analysis).
[0048] QDs may be capped with the ligands described above (e.g.
poly(oxyethylene glycol).sub.350 monomethyl ether acetic acid)
using any one of a number of suitable methods known to the skilled
person, which may optionally include ligand exchange and/or ligand
interchelation methodologies.
[0049] The invention may be embodied in other specific forms
without departing form the spirit or essential characteristics
thereof. The foregoing embodiments are therefore to be considered
in all respects illustrative rather than limiting on the invention
described herein. Scope of the invention is thus indicated by the
appended claims rather than by the foregoing description, and all
changes that come within the meaning and range of equivalency of
the claims are intended to be embraced therein.
* * * * *